Torsional vibration damping means for marine propulsion device

Abstract

An outboard drive having an improved arrangement for absorbing torsional vibrations and isolating the drive shaft from them. Several embodiments of torsional vibration dampers are disclosed each of which includes a first member that is detachably connected to the drive shaft and an inertial member that is coupled to the first member. In some embodiments, this coupling is achieved by an elastomeric sleeve and in others it is achieved by means of a viscous fluid.

We claim: 
     
       1. In a marine outboard drive comprising a power head containing an internal combustion engine having an output shaft, a flywheel drive from one end of said output shaft, a drive shaft housing depending from said power head and journaling a drive shaft driven by the other end of said output shaft, a lower unit containing propulsion means for propelling an associated watercraft and means for driving said propulsion means from said drive shaft, the improvement comprising torsional vibration damping means directly connected to said drive shaft for reducing the effects of torsional vibrations on said drive shaft, said torsional vibration damping means comprising a first annular member detachably affixed for rotation with said drive shaft, an annular inertial member axially aligned with said first annular member and rotatably relative to said drive shaft, and means for coupling said inertial member to said first member for relative movement therebetween. 
     
     
       2. In a marine outboard drive as set forth in claim 1 wherein the coupling means comprises an elastomeric element disposed radially between said first annular member and said inertial member. 
     
     
       3. In a marine outboard drive as set forth in claim 2 wherein the first member has a keyed connection to the drive shaft and the inertial member comprises an annular member, the elastomeric element comprising an elastomeric sleeve interconnecting said first member with said inertial member. 
     
     
       4. In a marine outboard drive as set forth in claim 3 further including means for axially affixing the first member to the drive shaft independent of the keyed connection. 
     
     
       5. In a marine outboard drive as set forth in claim 4 wherein the means for axially affixing the first member to the drive shaft comprises a shoulder formed integrally on the drive shaft. 
     
     
       6. In a marine outboard drive as set forth in claim 4 wherein the means for axially affixing the first member to the drive shaft comprises a pair of snap rings. 
     
     
       7. In a marine outboard drive as set forth in claim 1 wherein the coupling means comprises a fluid connection. 
     
     
       8. In a marine outboard drive as set forth in claim 7 wherein the first member defines an annular cavity and the inertial member is received in the annular cavity and has an annular configuration, the area between the annular cavity and the inertial member being at least partially filled with a viscous fluid. 
     
     
       9. In a marine outboard drive as set forth in claim 8 wherein the inertial member has vanes formed thereon for cooperating with the viscous fluid for increasing the effective inertia of the inertial member. 
     
     
       10. In a marine outboard drive comprising a drive shaft housing journaling a drive shaft driven by a power source, a lower unit containing propulsion means for propelling an associated watercraft and means for driving said propulsion means from said drive shaft, the improvement comprising torsional vibration damping means directly connected to said drive shaft for reducing the effects of torsional vibrations on said drive shaft, said torsional vibration damping means comprising a first member detachably affixed to said drive shaft, an inertial member, and means for coupling said inertial member to said first member for relative movement therebetween, said inertial member being immersed in a body of water and having vanes for cooperating with the water for dissipating heat and for increasing its effective inertia. 
     
     
       11. In a marine outboard drive as set forth in claim 10 wherein the power source comprises a crankshaft having a vertically extending axis and the drive shaft is driven at the lower end of said crankshaft, and further including a flywheel affixed to the upper end of said crankshaft.